Abstract's details
The Spatial Resolution of AVISO Gridded Sea Surface Height Fields
CoAuthors
Event: 2014 Ocean Surface Topography Science Team Meeting
Session: Near Real Time Products and Applications and Multi-Mission, Multi-Sensor Observations
Presentation type: Type Oral
Contribution: PDF file
Abstract:
The sea surface height (SSH) fields produced by AVISO are constructed by interpolating the measurements from multiple simultaneously operating altimeters onto a global 0.25° latitude by 0.25° longitude grid. The scales of the features that are resolved in these objectively analyzed SSH fields can be quantified by wavenumber spectral analysis. Previous analysis of the so-called "Reference" SSH fields (referred to as REF) that were constructed by AVISO from two simultaneously operating altimeters for the period October 1992-December 2008 found that the feature resolution was about 2° in longitude by 2° in latitude (Chelton et al., 2011, Prog. Oceanogr.). This corresponds to an e-folding eddy radius of approximately 0.4°, or roughly 40 km.
Wavenumber spectra have also previously been computed from the "Updated" (UPD) SSH fields constructed by AVISO from all available altimeters. Attention was focused on the 3-year period October 2002 through September 2005 during which four altimeters were operating nearly simultaneously. The spectra revealed that the UPD SSH fields also have a feature resolution of about 2° in longitude by 2° in latitude. The reason for the lack of improvement of feature resolution is that the same objective analysis procedure was used for both the REF and the UPD SSH fields with no change in the parameters of the objective analysis (in particular, the correlation length scales). The largest differences between the REF and UPD SSH fields occur in the small diamond centers formed by the interleaved tandem 10-day repeat orbits. This is evidence of improved accuracy of the UPD SSH fields, albeit with little improvement in resolution.
In this presentation, the newly available DT-2014 REF and UPD SSH fields produced by AVISO will be compared with the previous versions of the AVISO SSH fields to quantify improvements of the feature resolution and the accuracies of the SSH fields. This assessment of the DT-2014 SSH fields will be made from zonal and meridional wavenumber spectra computed from the gridded SSH fields and from maps of the mean and standard deviation of the differences from the previous AVISO SSH fields.
We will also assess the feature resolution of several experimental SSH datasets constructed from multi-mission altimeter data with modified parameters of the objective analysis procedure. A preliminary analysis of these fields concludes that improvements in feature resolution can be achieved, especially at low latitudes.
Wavenumber spectra have also previously been computed from the "Updated" (UPD) SSH fields constructed by AVISO from all available altimeters. Attention was focused on the 3-year period October 2002 through September 2005 during which four altimeters were operating nearly simultaneously. The spectra revealed that the UPD SSH fields also have a feature resolution of about 2° in longitude by 2° in latitude. The reason for the lack of improvement of feature resolution is that the same objective analysis procedure was used for both the REF and the UPD SSH fields with no change in the parameters of the objective analysis (in particular, the correlation length scales). The largest differences between the REF and UPD SSH fields occur in the small diamond centers formed by the interleaved tandem 10-day repeat orbits. This is evidence of improved accuracy of the UPD SSH fields, albeit with little improvement in resolution.
In this presentation, the newly available DT-2014 REF and UPD SSH fields produced by AVISO will be compared with the previous versions of the AVISO SSH fields to quantify improvements of the feature resolution and the accuracies of the SSH fields. This assessment of the DT-2014 SSH fields will be made from zonal and meridional wavenumber spectra computed from the gridded SSH fields and from maps of the mean and standard deviation of the differences from the previous AVISO SSH fields.
We will also assess the feature resolution of several experimental SSH datasets constructed from multi-mission altimeter data with modified parameters of the objective analysis procedure. A preliminary analysis of these fields concludes that improvements in feature resolution can be achieved, especially at low latitudes.